Novel polyimides, and polyamic acid and ester intermediates thereof

ABSTRACT

Novel polyimides, optionally end-capped with polymerizable or inert groups, and the polyamic acid or ester intermediates thereof are prepared by reacting a tetracarboxylic acid compound (e.g. pyromellitic dianhydride or 3,3&#39;,4,4&#39;-benzophenone tetracarboxylic acid dianhydride or its methyl diester) with diamines having the general formula ##STR1## wherein Z is oxygen or sulfur, X and/or Y are carbonyl or carbinol groups, the amine groups may be in the 2-, 3-, and/or 4-position, and isomerism is present when X and/or Y is a carbinol group. The polyimides may be end-capped by reaction, during or after their formation, with polymerizable groups such as 3-aminophenyl acetylene or 3,6-endomethylene-1,2,3,6-tetrahydrophthalic anhydride. The diamines are novel classes of amines when Z is sulfur and when Z is oxygen and X, Y, or X and Y are carbinol groups.

BACKGROUND OF THE INVENTION

This invention relates to novel polyimides, to end-capped polyimides,and to the polyamic acid and ester intermediates thereof. It alsorelates to their use as adhesives or molded articles. It further relatesto novel primary aromatic diamines for use in the preparation of thepolymers.

Polyimides are synthetic organic resins characterized by repeating imidelinkages in the polymer chain which may or may not be end-capped withpolymerizable or inert (i.e. non-polymerizable) chemical groups. Theyare available in both linear and crosslinked forms and are noted fortheir outstanding chemical and physical properties, particularly theirhigh temperature oxidative stability and strength. In addition to theiruse as adhesives and molded articles, they may be used as precured filmsand fibers, curable enamels, and laminating resins.

The polyimides, especially the preferred aromatic polyimides, areextremely difficult to process due to their insolubility and extremelyhigh softening points. Early attempts to decrease the softeningtemperature usually involved the substitution of aliphatic segments intothe otherwise aromatic polymers, but this generally resulted in anaccompanying decrease in thermooxidative stability. In order to overcomethese disadvantages and to improve their processability and mechanicalproperties, it has been found advantageous to introduce flexibilizingmoieties, such as bipyridyl, sulfone, alkylene, or preferably ether orthio bridges, into the polymer chain and thus provide a product withimproved flexibility and impact strength. Crosslinking moieties havealso been introduced into the polymers by the use of some portion of amore highly functional amine (e.g. triamine) or by the introduction ofcarboxyl or hydroxyl groups.

A further disadvantage exists if the polyamic acid or esterintermediates will not be used immediately. The solutions, preferablyconcentrated, must be stored at low temperatures and protected frommoisture to prevent premature imidization (i.e. ring closure). Inaddition, during curing to the fully or partially imidized resin, asappreciable amount of a volatile by-product (e.g. water, alcohol, orhydrohalides depending upon the starting tetracarboxylic acid compound)is formed. This leads to the formation of voids when the resin is usedas an adhesive between metal substrates or for forming molded articles.In order to overcome these disadvantages, low molecular weightpolyimides encapped with polymerizable groups such as ethylenicallyunsaturated groups, have been prepared. These end-capped polyimides canbe subsequently cured to void-free, higher molecular weight resins sinceno volatile by-product is formed.

It is a purpose of this invention to provide novel linear, optionallycrosslinked, polyimides which contain flexibilizing moieties and whichmay be, if desired, end-capped with polymerizable or inert groups. It isalso an object to provide improved adhesives and molded articles. It isa further object to provide novel primary aromatic diamines for use inthe preparation of the polyimides and the polyamic acid or esterintermediates.

SUMMARY OF THE INVENTION

In the first embodiment herein, the novel polyimides are prepared byreacting a tetracarboxylic acid compound, e.g. dianhydrides ordiester-diacids, with selected primary aromatic diamines containing athio or ether bridge, as well as carbonyl and/or carbinol bridges.Typically the reaction is carried out in an inert organic solvent at atemperature which will depend upon the tetracarboxylic compound used.The solution containing the soluble polyamic acid or ester intermediateis heated to a temperature sufficient to effect ring closure to thecorresponding polyimide and, if desired, to remove the solvent as wellas the by-product(s). If the polyamic acid or ester is insoluble or haspartially imidized and come out of solution, it can be recovered andthen converted to the fully imidized form by heating.

These polyimides are characterized by having recurring units of theformula --A--B)_(n), wherein A is ##STR2## wherein B is ##STR3## whereinR may be an aliphatic organic tetravalent radical containing at leasttwo carbon atoms with no more than two carbonyl groups being attached toany one carbon atom of said tetravalent radical or wherein R may be acycloaliphatic or aromatic tetravalent radical containing at least onering with the four carbonyl groups being attached directly to separatecarbon atoms in one or two rings of said radical and with each pair ofcarbonyl groups being attached to adjacent carbon atoms in said ring orrings of said radical; wherein Z is oxygen or sulfur; wherein X and/or Ymay be a carbonyl (CO) or carbinol (CHOH) group; wherein the nitrogensmay be independently attached to the benzene rings in the 2-, 3-, or4-positions; wherein isomerism is present when X and/or Y is a carbinolgroup; and wherein n is greater than 1 and equals the number of mers permolecule.

The corresponding polyamic acid and ester intermediates have recurringunits of the formula --A'--B)_(n), wherein A' is ##STR4## wherein R¹ andR² may be hydrogen or the same or different hydrocarbon monovalentradicals and wherein B, R, the nitrogen positions, and n are defined ashereinabove.

The primary aromatic diamines have the formula ##STR5## wherein theamine groups may be independently attached to the benzene rings in the2-, 3-, or 4-positions and wherein X, Z and Y are as definedhereinabove. All the diamines containing the thio linkage are novelcompounds prepared by hydrogenating the corresponding nitro compounds,preferably first to the corresponding carbonyl-containing diamine andsubsequently to the corresponding carbinol-containing diamine or mixedcarbonyl- and carbinol-containing diamine. The diamines containing theether linkage are novel compounds when one or two carbinol groups arepresent; they are prepared in a similar manner to the diaminescontaining the thio linkage.

In the second embodiment herein, novel end-capped polyimides areprepared by reacting a tetracarboxylic acid compound, e.g. dianhydride,with the selected primary aromatic diamines discussed hereinabove andwith a polymerizable or inert monoanhydride and/or a polymerizable orinert primary monoamine which act as the end-capping groups. When apolymerizable monoanhydride or monoamine is used, it is preferred toform a low molecular weight polyimide prior to reaction with theendcapping reagent. Typically, the reaction is carried out in an organicsolvent at a low or moderately elevated temperature. The stable, solublepolyimides end-capped with polymerizable groups may then be heated toinitiate the addition polymerization and the formation of the highermolecular weight polymers.

The end-capped polyimides have one or more of the formulas R³--A--B)_(m) R⁴, or R³ --A--B)A--R³, or R⁴ --B--A--B)_(m) R⁴, wherein Ais ##STR6## wherein R³ is an inert or polymerizable monovalent organicradical derived from an aliphatic, cycloaliphatic, aromatic, orheterocyclic primary monoamine; R⁴ is an inert or polymerizable divalentorganic radical derived from an aliphatic, cycloaliphatic, or aromaticmonoanhydride; wherein m equals the number of mers per molecule and m isone or greater; and wherein B and R are as defined hereinabove.

The end-capped polyamic intermediates have one or more of the formulasR³ --A'--B)_(m) R⁴, or R³ --A'--B)_(m) A'--R³, or R⁴ --B--A'--B)_(m) R⁴,wherein A' is ##STR7## and wherein B, R, R¹, R², R³, R⁴, and m are asdefined hereinabove.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preparation of the Diamines

The classes of primary aromatic diamines for use herein include4,4'-bis(aminobenzoyl)diphenyl ether and the novel ether derivatives4,4'-bis[(aminophenyl)hydroxymethyl]diphenyl ether and4-(aminobenzoyl)-4'-[(aminophenyl)hydroxymethyl]diphenyl ether, as wellas all the corresponding classes of novel thio ethers. The diamines maybe prepared by any of the methods conventionally used to preparearomatic primary amines, such as reduction of the nitro compound orreaction of aryl halides with ammonia. Reduction of the nitro compoundsis the simplest and most satisfactory method, and it may be accomplishedby catalytic hydrogenation using molecular hydrogen or by chemicalreduction using a metal and an acid. Hydrogenation is the preferredmethod since the dinitro compounds are quantitatively reduced to thediamine compounds; this is an important requirement for obtaining highmolecular weight polymers.

The compounds useful as precursors for the aromatic diamines herein maybe prepared in very high yields by reacting a 2-, 3-, or 4-nitrobenzoylhalide or mixtures thereof with diphenyl ether or diphenyl sulfide inthe presence of aluminum chloride or other Lewis acid to give thecorresponding dinitro compound which is subsequently reduced.Alternatively, a 2-, 3-, or 4-halonitrobenzoyl halide or mixturesthereof may be reacted with diphenyl ether or diphenyl sulfide to givethe corresponding dihalogen compound which is subsequently treated withammonia.

Hydrogenation of 4,4'-bis(3-nitrobenzoyl)diphenyl ether under mildconditions using palladium on charcoal as the catalyst reduces only thenitro groups leaving the carbonyl groups intact. Subsequent reduction ofthe diamine using sodium borohydride as the catalyst reduces bothcarbonyl groups to carbinol groups. Hydrogenation of the correspondingthio ether using palladium on charcoal reduces only the nitro groupsleaving the carbonyl groups intact. Hydrogenation of4,4'-bis(4-nitrobenzoyl)diphenyl ether using palladium on charcoalreduces, not only the nitro groups, but also some carbonyl groups andthe resulting amine is a mixture. The diamines containing carbinolgroup(s) are a mixture of stereoisomers (R, L, and meso) due to thepresence of one (or two) asymmetric carbon atoms in the chain.

By selecting suitable catalysts and reaction conditions the skilledpractitioner can selectively reduce only nitro groups to amine groups,subsequently reduce the carbonyl groups to carbinol groups or to adiamine mixture containing carbinol as well as carbonyl groups, orsimultaneously reduce the nitro and carbonyl groups.

Preparation of the Polyimides and Polyamic Acid or Ester Intermediates

One or more of the diamines described herein above are reacted in asuitable inert organic solvent with one or more tetracarboxylic acidcompound selected from the following group:

    ______________________________________                                        (a) dianhydrides of the formula                                                                  ##STR8##                                                   (b) tetraacids of the formula                                                                    ##STR9##                                                   (c) tetraesters of the formula                                                                   ##STR10##                                                  (d) diester-diacids of the formula                                                               ##STR11##                                                  (e) dihaloformyldiesters of the formula                                                          ##STR12##                                                  ______________________________________                                    

wherein R is the tetravalent organic radical as hereabove defined; R⁵and R⁶ may be the same or different hydrocarbon monovalent radicals,each preferably containing from 1 to 13 carbon atoms (e.g. C₁ -C₁₃ alkylradicals or C₆ -C₁₃ cycloalkyl or aryl radicals); X is a halogen atom,preferably chlorine or bromine; and the arrows indicate isomerism.

Typical dianhydrides suitable for use herein include, for example,2,2',3,3'-, 2,3,3',4'-, or 3,4,3',4'-benzophenone tetracarboxylic aciddianhydride, pyromellitic dianhydride, 2,2',3,3'- or 3,3',4,4',biphenyltetracarboxylic acid dianhydride, thiophene2,3,4,5-tetracarboxylic acid dianhydride,2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, bis(3,4-dicarboxyphenylsulfone dianhydride, perylene 3,4,9,10-tetracarboxylic acid dianhydride,ethylenetetracarboxylic acid dianhydride, 1,2,3,4-butanetetracarboxylicacid dianhydride, bis(3,4,dicarboxyphenyl)ether dianhydride, and thelike. A more extensive listing of suitable dianhydrides may be found inU.S. Pat. No. 3,699,074 issued Oct. 17, 1972 to H. R. Lubowitz et al.Suitable tetracarboxylic acids are listed in U.S. Pat. No. 3,678,005issued July 18, 1972 to G. Rabilloud et al. Diester diacids derived fromthe above dianhydrides by reaction with an alcohol are also suitable foruse herein.

Reaction conditions used for the preparation of the intermediate willdepend, not only upon the aromatic diamine used, but more particularlyon the tetracarboxylic acid compound used. It will also depend upon thesolvent selected and the percentage and molecular weight of theintermediate desired in the final solution. The preferred methods ofpreparing the polyamic acid or ester intermediates are by reaction ofdiamines with either dianhydrides or diester-diacids derived from loweralcohols. The reactions are carried out under anhydrous conditionspreferably using pure monomers and dry solvents.

The solvents used should dissolve at least one of the reactants,preferably both the dianhydride and diamine. Provided imidization hasnot proceeded too far and provided the intermediate is soluble, thesolvent should maintain the polyamic acid or ester in solution. Suitablesolvents include, for example, N,N-dimethylformamide,N,N-dimethylacetamide, dimethyl sulfoxide, 1-methyl-2-pyrrolidinone,tetramethylurea, and the like. These solvents can be used alone or incombination with other solvents such as benzene, benzonitrile, dioxane,xylene, toluene, and cyclohexane.

The diamine-dianhydride reaction is relatively rapid at lowtemperatures. It is typically carried out by first dissolving thediamine in the dry solvent, adding the powdered dianhydride or a dilutesolution thereof in portions while applying external cooling, andmaintaining the temperature at about 10°-60° C. for about 1 to 6 hours.If pyromellitic dianhydride is used, a somewhat higher temperature maybe required to dissolve the dianhydride (preferably below 75° C.).

In a preferred method, the dianhydride is first reacted with ananhydrous lower alcohol, such as methanol or ethanol, to form thecorresponding diester-diacid. The diamine and solvent are then added andthe excess alcohol distilled off. Alternatively, the diester-diacid maybe recovered from the excess alcohol and then added to the dissolveddiamine or both diamine and diester-diacid may be separately dissolvedand combined. The reaction mixture is heated at about 100°-150° C.,while continuing to distill off alcohol and water, until the desiredmolecular weight is reached at which point the reaction vessel iscooled. Since the polymerization does not proceed at lower temperatures,the molecular weight is controlled by the time and temperature ofreaction. If desired, a low molecular weight intermediate may be formedand then post cured, during use, to the higher molecular weightintermediate prior to full imidization. Alternatively, a high molecularweight intermediate, which requires no post cure, can be prepared.

Generally the polyamic acid or ester intermediate is obtained at 40 to70% solids when low molecular weight intermediates are formed and at 10to 40% solids when high molecular weight intermediates are formed. Thesolution stability of the intermediates is sensitive to temperature,concentration, and moisture. Concentrated solutions are more stable thandilute solutions and can be stored for long periods at low temperaturesif protected from moisture.

After formation of the polyamic acid or ester intermediate, thepolyimide is obtained by heating the intermediate to about 300° C. or bytreating the intermediate with chemical cyclizing agents at temperaturesof about 100° C. or lower. Typical cyclizing agents include adehydrating agent (e.g. acetic anhydride) in combination with a basiccatalyst (e.g. pyridine) or a carbodiimide (e.g.dicyclohexylcarbodiimide). A combination of chemical and thermalcyclization may be used.

Preparation of the End-Capped Polyimides

The end-capped polyimides are prepared by coreacting stoichiometricequivalents of one or more of the above dianhydrides, one or more of theabove diamines, and selected primary monoamines and/or monoanhydrides.The molecular weight is controlled by the stoichiometry. Preferably, themonoamine and/or monoanhydride should be present in an amount sufficientto completely end-cap the polymer depending upon its molecular weight.It is thus essential that the total chemical equivalents of primaryamine (i.e. diamine or diamine plus monoamine) equal the totalequivalents of anhydride (i.e. dianhydride or dianhydride plusmonoanhydride). If both end groups are not to be capped, then equivalentamounts of primary amine and anhydride are not necessary.

The monoanhydrides and monoamines suitable for use herein are thosewhich are inert or thermally polymerizable by an addition reaction sothat no volatile gases are formed as a by-product. Typical of suchpolymerizable monofunctional reactants areendo-cis-5-norbornene-2,3-dicarboxylic anhydride, often called Nadicanhydride(trademark of Allied Chemical Co.),maleic anhydride,3-aminophenyl acetylene, 3-cyanoaniline, and the like. Typical inertmonofunctional reactants are phthalic anhydride, 4-acetamido-phthalicanhydride, 4-acetamido-aniline, and the like.

Polymerization to low molecular weight, substantially completelyimidized polymers can be carried out in two or three steps using theconventional reaction conditions and solvents discussed hereinabove.Preferably, the dianhydride and diamine are reacted in a suitablesolvent to form a comparatively low molecular weight, soluble polyamicacid or ester intermediate; then the intermediate is reacted with themonofunctional reactant(s) to end-cap the intermediate; and finally theend-capped intermediate is imidized until ring closure is substantiallycomplete as indicated by the cessation of the formation of volatileby-product(s). If the dianhydride, diamine, and monofunctional reactantare polymerized in one step, it is more difficult to control themolecular weight and insoluble intermediates and/or insoluble fullyimidized polymers may be formed. It may be possible to recover theinsoluble resin, to isolate the soluble resin by coagulation with amiscible, non-solvent such as water, and to blend various proportions ofthe two resins in the presence or absence of a liquid vehicle. If aliquid is used, it is removed prior to thermal conversion (curing) tothe higher molecular weight addition polymer. The purpose of the blendis to form a homogeneous mass which can be fused at a temperature belowthat at which the end-capped polyimide homopolymerizes.

Curing of the end-capped polymer may be achieved at moderately hightemperatures (e.g. about 175°-600° C.), if necessary with the use ofmoderate to high pressure (about 15-1000 p.s.i.). The conditionsrequired will, of course, depend upon the monofunctional reactant(s)used. In some cases, a catalyst may facilitate the cure or a post-cureafter the desired application may be desirable.

Use of the Resins

Both the thermoplastic and thermosetting resins, which may or may not befully imidized and which may or may not be crosslinked depending uponthe presence or absence of carbinol groups, can be used as moldings oradhesives.

The resulting polyamic acid or ester solutions or end-capped polyimidesolutions herein, which are usually smooth viscous solutions, can beapplied to suitably prepared substrate surfaces; if desired, they may beformulated with fillers, thickeners, pigments, etc. They may be usedwith or without supports such as glass fabric. Alternatively, they maybe cast into a film from solution and then applied or even applied as aslurry or melt. If necessary, the substrates are allowed to stand topermit some or all of the solvent to evaporate. The treated surfaces tobe bonded are assembled together by means of a clamp or press and theassembled substrates are heated. If a polyamic acid or ester is used,the assembled substrates are heated to a temperature above theintermediate's glass transition temperature for a time sufficient toeffect ring closure, to volatilize the by-product formed, and, ifnecessary, to volatize some or all of the solvent. If a polymerizableend-capped polyimide is used, the assembled structures are heated to atemperature sufficient to activate the end groups and form the highmolecular weight addition polymer. If fully imidized and/or polymerizedto the desired degree prior to application, no post cure afterapplication is needed. A post cure may be desirable to effectcrosslinking in the polyimides containing carbinol groups. Because theadhesives adhere to a variety of different materials, including metals,non-metals, ceramics, etc., they may be utilized in a large number ofapplications.

The resins can also be used to form filled or unfilled molded articles.The end-capped polyimide resins are especially useful for preparingmolded articles since the subsequent curing does not form a volatileby-product and the molded articles are void-free. Compression moldingtemperatures will depend upon whether the resin is thermoplastic orthermosetting. Thermosetting resins are typically heated at about330°-350° C. and about 3000-5000 p.s.i., and the resin is kept in themold for at least 5 minutes for good flow prior to cooling to about 250°C. or less for demolding. Thermoset resins and some thermoplastics thatbehave like thermosets can be compression molded at about 218° C./3000p.s.i. in 2-10 minute cycles, transfer molded at about 193° C./3000p.s.i. in 1-5 minute cycles, injection molded at about 10,000 p.s.i. in60 second cycles with mold temperatures of about 238° C. and barreltemperatures of about 93° C., or free sintered to about 249° C. after a15 second/15,000 p.s.i. cold forming.

It can be appreciated by the practitioner that a large number ofvariations may be effected in the selection of tetracarboxylic acidcompounds and in the preparation and use procedures described hereinwithout materially departing from the scope and spirit of the invention.Such variations will be apparent to those skilled in the art and are tobe included within the scope of this invention.

The following examples will more fully illustrate the embodiments ofthis invention. In the examples, all parts and percentages are given byweight and all temperatures are in degrees Celsius, unless otherwisenoted. Inherent viscosities were determined on 1 g./dl. solutions at 25°C. in a mixture of 86% 1-methyl-2-pyrrolidinone and 14% methanol unlessotherwise noted. The lap shear strength was determined using chromicacid treated aluminum panels having the dimensions 2.54 cm. by 15.2 cm.by 0.16 cm. A small amount of the polymer solution was applied to thesurface of one panel near one edge. The second panel was pressed againstthe first to form an adhesive film such that there was a 1.27 cm.overlap for each panel and hence a bonding area of 3.22 cm.². The panelswere clamped together by means of a spring clip, and dried at 150° C.and cured at 275° C. After equilibration to ambient temperature, thepanels were pulled apart with an Instron Tensile Tester at a crossheadoperation speed of 0.05 in./min. The values given were the average oftwo determinations.

EXAMPLE I

This example describes the preparation of a polymer by the reaction of4,4'-bis(3-aminobenzoyl)diphenyl ether with the methyl diester of3,3',4,4'-benzophenone tetracarboxylic acid and its use as an adhesive.It also describes the preparation of 4,4'-bis-(3-nitrobenzoyl)-diphenylether and its subsequent reduction to the corresponding diamine.

A total of 242.7 parts (1.82 moles) of aluminum chloride was added over1 hr. to a cooled solution of 102.1 parts (0.60 mole) diphenyl ether and233.8 parts (1.26 moles) 3-nitrobenzoyl chloride in 600 ml. of1,2-dichloroethane. The temperature was maintained at between 10°-20° C.during the addition. The mixture was then slowly heated to the boilingpoint and refluxed for 3 hr. The solution was cooled and poured into1700 ml. of a mixture of ice water and concentrated hydrochloric acid(7.5:1). The aqueous layer was decanted off. The product was washed with1000 ml. ethanol, filtered, dried, and recrystallized from methylisobutyl ketone. The resulting 4,4'-bis(3-nitrobenzyl)-diphenyl etherhad a melting point of 174°-175° C. (literature 175° C.).

A total of 70.2 parts (0.15 mole) of the above dinitro compound in 550ml. dioxane was hydrogenated at 70°-80° C. using 3.6 parts of 5%palladium on charcoal as the catalyst. Hydrogenation was continued untilhydrogen absorption ceased. The solution was filtered, and the productwas precipitated by the addition of 500 ml. water. The resulting4,4'-bis(3-aminobenzoyl)diphenyl ether had a melting point of 131°-133°C. (literature 150°-151° C.); NMR analysis indicated that the carbonylgroups were unaffected by the reduction.

A mixture of 9.67 parts (0.03 mole) of 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride and 20 ml. of methanol was refluxed for2 hr. with stirring to form the corresponding methyl diester. A total of12.25 parts (0.03 mole) of the above diamine and 18 parts of1-methyl-2-pyrrolidinone was added, and the mixture was heated under anitrogen atmosphere at 77°-125° C. for 7 hr. The distillate wascollected in a 25 ml. Dean-Stark receiver. The resulting polymer had aninherent viscosity of 0.20 dl./g. It was used to bond chromic acidtreated aluminum panels using the procedure previously described. Theadhesive's lap shear strength was 2640 p.s.i.

EXAMPLE II

This example describes the preparation of a polymer by the reaction ofpyromellitic dianhydride and the diamine of Example I.

A total of 8.17 parts (0.02 mole) of 4,4'-bis(3-aminobenzoyl)diphenylether in 30 parts 1-methyl-2-pyrrolidinone was treated over a 7 min.period with 4.36 parts (0.02 mole) of pyromellitic dianhydride. Theresidual dianhydride was washed in with 7 parts of1-methyl-2-pyrrolidinone. The temperature rose to about 35° C. andgradually dropped back to ambient temperature. The solution was stirredfor 5 hr. The resulting polymer had an inherent viscosity of 0.54 dl./g.in 1-methyl-2-pyrrolidinone. It was used as an adhesive as previouslydescribed; the lap shear strength was 880 p.s.i.

EXAMPLE III

This example describes the preparation of the novel diamine4,4'-bis[(3-aminophenyl)hydroxymethyl]diphenyl ether and itspolymerization with the methyl diester of 3,3',4,4'-benzophenonetetracarboxylic acid.

A cooled solution (0.08 mole) of 32.6 parts of4-4'-bis(3-aminobenzoyl)diphenyl ether (see Example I for thepreparation thereof) in 200 ml. tetrahydrofuran was treated over a 1.5hr. period with a solution of 6.05 parts (0.16 mole) sodium borohydridein 80 ml. water. The reaction mixture was maintained at room temperaturefor 3 days and then diluted with 100 ml. water. The solvent was removedby vacuum distillation. The product was dissolved in 200 ml. methylethyl ketone, washed with water, dried over magnesium sulfate, andprecipitated by the addition of 3 volumes of cyclohexane. It wasdissolved in methanol and vacuum dried to yield 28.8 parts of a mixtureof stereoisomers of 4,4'-bis[(3-aminophenyl)hydroxymethyl]diphenyl etherhaving a melting point of 55°-66° C.

The polymerization was carried out using the procedure described inExample I except that the mixture was heated for only 1.5 hr. sincelonger heating times led to gellation of the polymer. The amounts ofreactants used were 9.67 parts (0.03 mole) 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride, 20 ml. methanol, and 12.37 parts (0.03mole) of the above diamine in 22 parts 1-methyl-2-pyrrolidinone. Theresulting polymer had an inherent viscosity of 0.28 dl./g.

EXAMPLE IV

This example describes the preparation of a novel diamine mixturecontaining some carbinol groups and its polymerization with the methyldiester of 3,3',4,4'-benzophenone tetracarboxylic acid. It alsodescribes the preparation of 4,4'-bis(4-nitrobenzoyl)diphenyl ether andits subsequent reduction to the corresponding diamine mixture.

4-Nitrobenzoyl chloride was reacted with diphenyl ether using thequantities and procedure of Example I. The resulting4,4'-bis(4-nitrobenzoyl)diphenyl ether was recrystallized fromγ-butyrolactone; it had a melting point of 230°-232° C. (literature 226°C.).

A total of 58.5 parts (0.125 mole) of the above dinitro compound in 500ml. dimethylformamide was hydrogenated at 60°-70° C. in the presence of3 parts of 5% palladium on charcoal until the rate of hydrogen uptakedecreased. The product was precipitated by the addition of 1000 ml. ofwater. The yield was 38.5 parts (75.5%). The resulting diamine, whichwas probably a mixture of 4,4'-bis(4-aminobenzoyl)-diphenyl ether(literature m.p. 177°-178° C.) and the novel diamines4-(4-aminobenzoyl)-4'-[(4-aminophenyl)hydroxymethyl]diphenyl ether,4-[(4-aminophenyl)hydroxymethyl)]-4'-(4-aminobenzoyl)diphenyl ether, and4,4'-bis[(4-aminophenyl)hydroxymethyl]diphenyl ether, had a meltingpoint of 152°-154° C. NMR analysis indicated that about 10% of thecarbonyl groups were reduced to carbinol groups.

The polymerization was carried out using the procedure described inExample I except that the mixture was heated for only 1.5 hr. The amountof reactants used was 9.67 parts (0.03 mole) 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride, 20 ml. methanol, and 12.24 parts (0.03mole) of the above diamine mixture in 22 parts 1-methyl-2-pyrrolidinone.The resulting polymer had an inherent viscosity of 0.15 dl./g. Whencured and evaluated as previously described, the adhesive had a tensilelap shear strength of 4200 p.s.i.

EXAMPLE V

This example describes the preparation of the novel diamine4,4'-bis(3-aminobenzoyl)diphenyl sulfide and its polymerization with themethyl diester of 3,3',4,4'-benzophenone tetracarboxylic acid. It alsodescribes the preparation of 4,4'-bis(3-nitrobenzoyl)diphenyl sulfideand its subsequent reduction to the novel diamine.

A mixture of 46.6 parts (0.25 mole) of diphenyl sulfide and 98.4 parts(0.53 mole) of 3-nitrobenzoyl chloride in 250 ml. 1,2-dichloroethane wastreated with 101.9 parts (0.76 mole) aluminum chloride using theprocedure described in Example I. The crude product was recrystallizedfrom γ-butyrolactone. The resulting 4,4'-bis(3-nitrobenzoyl)-diphenylsulfide had a melting point of 229°-230° C. (literature 229°-230° C.).

A total of 36.3 parts (0.075 mole) of the above dinitro compound in 375ml. dimethylformamide was hydrogenated at 100°-110° C. using 3.6 partsof 5% palladium on charcoal as the catalyst. The mixture was filtered,and the product was precipitated by the addition of 600 ml. of water.The resulting 4,4'-bis(3-aminobenzoyl)diphenyl sulfide had a meltingpoint of 163°-164° C. The yield was 30.3 parts (95.2%). NMR and infraredspectroscopy confirmed the presence of the carbonyl groups.

The polymerization was carried out using the procedure described inExample I except that the solution was cooled prior to the addition ofthe diamine and the final solution was heated for 1.5 hr. at 110°-145°C. after the removal of the excess methanol. The reactant amounts usedwere 6.44 parts (0.02 mole) 3,3',4,4'-benzophenone tetracarboxylic aciddianhydride, 13 ml. methanol, and 8.49 parts (0.02 mole) of the abovenovel diamine in 15 parts 1-methyl-2-pyrrolidinone. The resultingpolymer had an inherent viscosity of 0.15 dl./g. It was used as anadhesive as previously described; the lap shear strength was 2800 p.s.i.

EXAMPLE VI

This example describes the preparation of a polyimide of3,3',4,4'-benzophenone tetracarboxylic acid dianhydride and4,4'-bis-(3-aminobenzoyl)diphenyl ether which is end-capped with thepolymerizable primary monoamine 3-aminophenyl acetylene.

A solution of 8.06 parts (0.025 mole) 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride in 20 parts 1-methyl-2-pyrrolidinone atroom temperature was treated in portions with 8.17 parts (0.020 mole)4,4'-bis(3-aminobenzoyl)diphenyl ether (see Example I for thepreparation of this diamine). Residual diamine was washed in with 4parts 1-methyl-2-pyrrolidinone, and the reaction mixture was stirred for1 hr. at 50°-66° C. A total of 1.17 parts (0.010 mole) 3-aminophenylacetylene in 3 parts 1-methyl-2-pyrrolidinone was added, and thereaction mixture was allowed to remain overnight at ambient temperature.The flask was equipped with a 25 ml. Dean-Stark trap and 40 ml. oftoluene were added. The solution was refluxed for 6.5 hr. while thewater was collected and the toluene was returned. The toluene was thenremoved by vacuum distillation. The resulting end-capped polymer had aninherent viscosity of 0.12 dl./g.

EXAMPLE VII

This example describes the preparation of a polyimide of3,3',4,4'-benzophenone tetracarboxylic acid dianhydride and4,4'-bis-(3-aminobenzoyl)diphenyl ether which is endcapped with thepolymerizable monoanhydride endo-cis-5-norbornene-2,3-dicarboxylicanhydride. If one does not wish to form the polymerizable polyimide, thepolyimide may be end-capped with phthalic anhydride using the moleratios given below.

A solution of 10.21 parts (0.025 mole) 4,4'-bis(3-aminobenzoyl)-diphenylether in 20 parts 1-methyl-2-pyrrolidinone at 25° C. was treated with6.44 parts (0.020 mole) 3,3',4,4'-benzophenone tetracarboxylic aciddianhydride. Residual dianhydride was washed in with 3 parts1-methyl-2-pyrrolidinone, and the reaction mixture was stirred at21°-35° C. for 2.5 hr. A total of 1.64 parts (0.01 mole) ofendo-cis-5-norbornene-2,3-dicarboxylic anhydride was added followed by 3parts of 1-methyl-2-pyrrolidinone. The solution was left overnight atroom temperature, 40 ml. toluene were added, and the ring closure wascarried out as in Example VI. The end-capped polymer had an inherentviscosity of 0.23 dl./g.

Summarizing, this invention is seen to provide novel linear polyimides,optionally end-capped with inert or polymerizable monoanhydride and/ormonoamine groups, and the polyamic acid and ester intermediates thereof,as well as novel diamines for use in their preparation.

Now that the preferred embodiments of the present invention have beendescribed in detail, various modifications and improvements thereon willbecome readily apparent to those skilled in the art. Accordingly, thespirit and scope of the invention are to be limited only by the appendedclaims and not by the foregoing specification.

What is claimed is:
 1. A polyimide resin, consisting essentially of achain of chain of recurring units of the formula: ##STR13## wherein R isa tetravalent aliphatic, cycloaliphatic, or aromatic radical; Z isoxygen or sulfur; X and Y are carbonyl or carbinol groups and X and Ymay be the same or different; and n is greater than
 1. 2. A polyamicresin, consisting essentially of a chain of recurring units of theformula: ##STR14## wherein R is a tetravalent aliphatic, cycloaliphatic,or aromatic radical; R¹ and R² are hydrogen or the same or differenthydrocarbon monovalent radicals; Z is oxygen or sulfur; X and Y arecarbonyl or carbinol groups and X and Y may be the same or different;and n is greater than
 1. 3. The resin of claim 1 or 2, wherein Z isoxygen or sulfur and X and Y are carbonyl groups or wherein Z is oxygenand X and Y are carbinol groups or a mixture of carbonyl and carbinolgroups.
 4. The resin of claim 1 or 2, wherein R is the tetravalentradical having the formula ##STR15## X and Y are carbonyl groups, andboth nitrogens are in the 3-position; or wherein R is as defined above,Z is oxygen, X and Y are carbinol groups, and both nitrogens are in the3-position; or wherein R is as defined above, Z is oxygen, X and Y arecarbonyl groups, carbinol groups, or mixtures of carbonyl and carbinolgroups, and both nitrogens are in the 4-position; or wherein R is thetetravalent radical having the formula ##STR16## Z is oxygen, X and Yare carbonyl groups, and both nitrogens are in the 3-position.
 5. Anend-capped polyimide resin, having one or more of the formulas:##STR17## R is a tetravalent aliphatic, cycloaliphatic, or aromaticradical; or polymerizable is an inert of polymerizable monovalentaliphatic, cycloaliphatic, or aromatic radical; or polymerizable is aninert or polymerizable divalent aliphatic, cycloaliphatic, or aromaticradical; Z is oxygen or sulfur; X and Y are carbonyl or carbinol groupsand X and Y may be the same or different; and m is one or greater.
 6. Anend-capped polyamic resin, having one or more of the formulas: ##STR18##R is a tetravalent aliphatic, cycloaliphatic, or aromatic radical; R¹and R² are hydrogen or a monovalent hydrocarbon radical and R¹ and R²may be the same or different; R³ is an inert or polymerizable monovalentaliphatic cycloaliphatic, or aromatic radical; R⁴ is an inert orpolymerizable divalent aliphatic, cycloaliphatic, or aromatic radical; Zis oxygen or sulfur; X and Y are carbonyl or carbinol groups and X an Ymay be the same or different; and m is one or greater.
 7. The resinresulting from the polymerization of the composition of claim 5 or 6,wherein R³, R⁴, or R³ and R⁴ are polymerizable organic radicals.
 8. Theresin of claim 5 or 6, wherein R is the tetravalent radical having theformula ##STR19## Z is oxygen, X and Y are carbonyl groups, bothnitrogens are in the 3-position, and R³ is the monovalent radical havingthe formula ##STR20## or wherein R is as defined above, Z is oxygen, Xand Y are carbonyl groups, both nitrogens are in the 3-position, and R⁴is the divalent radical having the formula ##STR21##
 9. The resinresulting from the polymerization of the composition of claim 8.